If you just want to see how secure your network is or you would like to audit your own network, and to determine the insecurity of cleartext network protocols then you need to use sniffer programs. There are tons of Network protocol analyzer for Unix and Linux exist that allows examination of data from a live network, or from a capture file on disk For example Ethereal is one of such a program.

However, if you just interested in a password related auditing then nothing can beat dsniff program. It is simple and easy to use. dsniff capture passwords through http, ftp, smtp, pop3, telnet and many other cleartext protocols. dsniff includes various sniffing utilities for penetration testing.

Step # 1: Install dsniff

Install dsniff under Debian / Ubuntu Linux:# apt-get install dsniff If you are using FreeBSD then you can install it using ports or binary package:# pkg_add -r dsniff On the other hand, use ports collection:># cd /usr/ports/security/dsniff # make; make install; make clean

Step # 2: Start dsniff

dsniff automatically detects and minimally parses each application protocol, only saving the interesting bits, and uses Berkeley DB as its output file format, only logging unique authentication attempts. Login as a root user and type dsniff command:# dsniff For example, if user use ftp, telnet, or other cleartext protocol then you can capture passwords: Output: